False-positive reduction technique for detection of masses on digital mammograms: global and local multiresolution texture analysis

We investigated the application of multiresolution global and local texture features to reduce false-positive detection in a computerized mass detection program. One hundred and sixty-eight digitized mammograms were randomly and equally divided into training and test groups. From these mammograms, two datasets were formed. The first dataset (manual) contained four regions of interest (ROIs) selected manually from each of the mammograms. One of the four ROIs contained a biopsy-proven mass and the other three contained normal parenchyma, including dense, mixed dense/fatty, and fatty tissues. The second dataset (hybrid) contained the manually extracted mass ROIs, along with normal tissue ROIs extracted by an automated Density-Weighted Contrast Enhancement (DWCE) algorithm as false-positive detections. A wavelet transform was used to decompose an ROI into several scales. Global texture features were derived from the low-pass coefficients in the wavelet transformed images. Local texture features were calculated from the suspicious object and the peripheral subregions. Linear discriminant models using effective features selected from the global, local, or combined feature spaces were established to maximize the separation between masses and normal tissue. Receiver Operating Characteristic (ROC) analysis was conducted to evaluate the classifier performance. The classification accuracy using global features were comparable to that using local features. With both global and local features, the average area, Az, under the test ROC curve, reached 0.92 for the manual dataset and 0.96 for the hybrid dataset, demonstrating statistically significant improvement over those obtained with global or local features alone. The results indicated the effectiveness of the combined global and local features in the classification of masses and normal tissue for false-positive reduction.

Human tyrosyl-tRNA synthetase shares amino acid sequence homology with a putative cytokine

To test the hypothesis that tRNATyr recognition differs between bacterial and human tyrosyl-tRNA synthetases, we sequenced several clones identified as human tyrosyl-tRNA synthetase cDNAs by the Human Genome Project. We found that human tyrosyl-tRNA synthetase is composed of three domains: 1) an amino-terminal Rossmann fold domain that is responsible for formation of the activated E.Tyr-AMP intermediate and is conserved among bacteria, archeae, and eukaryotes; 2) a tRNA anticodon recognition domain that has not been conserved between bacteria and eukaryotes; and 3) a carboxyl-terminal domain that is unique to the human tyrosyl-tRNA synthetase and whose primary structure is 49% identical to the putative human cytokine endothelial monocyte-activating protein II, 50% identical to the carboxyl-terminal domain of methionyl-tRNA synthetase from Caenorhabditis elegans, and 43% identical to the carboxyl-terminal domain of Arc1p from Saccharomyces cerevisiae. The first two domains of the human tyrosyl-tRNA synthetase are 52, 36, and 16% identical to tyrosyl-tRNA synthetases from S. cerevisiae, Methanococcus jannaschii, and Bacillus stearothermophilus, respectively. Nine of fifteen amino acids known to be involved in the formation of the tyrosyl-adenylate complex in B. stearothermophilus are conserved across all of the organisms, whereas amino acids involved in the recognition of tRNATyr are not conserved. Kinetic analyses of recombinant human and B. stearothermophilus tyrosyl-tRNA synthetases expressed in Escherichia coli indicate that human tyrosyl-tRNA synthetase aminoacylates human but not B. stearothermophilus tRNATyr, and vice versa, supporting the original hypothesis. It is proposed that like endothelial monocyte-activating protein II and the carboxyl-terminal domain of Arc1p, the carboxyl-terminal domain of human tyrosyl-tRNA synthetase evolved from gene duplication of the carboxyl-terminal domain of methionyl-tRNA synthetase and may direct tRNA to the active site of the enzyme.

Relationship between adduct formation, rates of excision repair and the cytotoxic and mutagenic effects of structurally-related polycyclic aromatic carcinogens

The cytotoxic and mutagenic effect of 1-nitrosopyrene (1-NOP) and N-acetoxy-2-acetylaminofluorene (N-AcO-AAF) were compared with that of (+/-)-7 beta, 8 alpha-dihydroxy-9 alpha, 10-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene (BPDE) as a function of the initial frequency of adducts formed in the DNA of repair-proficient diploid human fibroblasts and the fraction remaining at the time the cells replicate their DNA. The principal adducts of all three agents involve guanine. The initial level of BPDE-, 1-NOP-, or N-AcO-AAF-induced adducts per 10(6) nucleotides required to lower the survival of these cells to 37% of the control was 8, 25, and 50, respectively. The frequency of mutants per 10(6) clonable cells induced at those levels of initial adduct formation was 160, 80, and 40, respectively. We determined the rate of excision repair of these adducts from the overall genome, from the individual strands of the hypoxanthine phosphoribosyltransferase (HPRT) gene, and in the case of 1-NOP and BPDE, at the level of individual nucleotides in the nontranscribed strand of exon 3 of that gene, a region where mutations induced by those agents are particularly frequent. 1-NOP-induced adducts were excised from the overall genome and from the individual strands of HPRT at a rate 2-3 times faster than BPDE-induced adducts. The average rate of repair of 1-NOP-induced adducts in exon 3 was also 2-3 times faster than the average rate of repair of BPDE-induced adducts. However, at particular nucleotides 1-NOP-induced adducts were repaired much faster, or slower, or in some cases at a rate equal to that of BPDE-induced adducts. Excision repair of N-AcO-AAF-induced adducts (i.e., deacetylated aminofluorene residues) was significantly slower than that of BPDE- or 1-NOP-induced adducts, and was not strand-specific. In an in vitro assay, BPDE adducts were four times more effective in blocking transcription than were 1-NOP or N-AcO-AAF-induced adducts. We conclude that the cytotoxic and mutagenic effect of these carcinogens reflect a complex interplay of adduct conformation, ability of adducts to block replication and transcription, and variation in the rate of excision repair, even at the nucleotide level.

Effect of nuclear environment on the distribution of benzo[a]pyrene diol epoxide-induced adducts in the HPRT gene of human fibroblasts

(+/-)-7beta,8alpha- Dihydroxy-9alpha,10alpha-epoxy-7,8,9,10-tetrahydrobenzo[a]py rene (BPDE) is the principal reactive metabolite of the carcinogenic environmental pollutant benzo[a]pyrene. Intensive studies of the distribution of BPDE-induced adduct formation in chromatin DNA compared to that in protein-free DNA have been conducted. However, until recently, investigation of BPDE-induced adduct formation at the nucleotide level in intact mammalian cells has not been feasible. We used ligation-mediated polymerase chain reaction (LMPCR) in conjunction with Escherichia coli UvrABC excinuclease to investigate the distribution of BPDE-induced adducts in the non-transcribed strand of exon 3 of the HPRT gene in normal human fibroblasts at the level of individual nucleotides to single nucleotide resolution using synchronized cell populations. We found that the relative distribution of BPDE adducts in the region of interest was essentially the same in cells treated in early G1 phase, S-phase, late G2/M phase, and in cells blocked at metaphase. Furthermore, for almost all nucleotide positions, the relative distribution of BPDE adducts in the intact cells was very similar to that found when purified DNA was treated with BPDE in vitro. The only exception was that in vivo, adduct formation at a region of six consecutive guanines, i.e. nucleotides 207-212, was strongly enhanced compared with that seen with DNA treated in vitro. No obvious nucleosomal structures or other protein-DNA interaction were detected within the region of interest by in vivo footprinting with micrococcal nuclease and other reagents revealed. In vitro studies mapping BPDE-induced adduct formation using Sequenase and UvrABC excinuclease suggested that this region of six consecutive guanines adopts a special DNA conformation. Therefore, we conclude that rather than reflecting protein-DNA interaction, the enhanced BPDE-induced adduct formation at nucleotides 207-212 in vivo reflects the impact of the physiological environment in the cell nucleus on the local DNA conformation, and that this effect remains constant throughout the cell cycle.

Automated detection of breast masses on mammograms using adaptive contrast enhancement and texture classification

This paper presents segmentation and classification results of an automated algorithm for the detection of breast masses on digitized mammograms. Potential mass regions were first identified using density-weighted contrast enhancement (DWCE) segmentation applied to single-view mammograms. Once the potential mass regions had been identified, multiresolution texture features extracted from wavelet coefficients were calculated, and linear discriminant analysis (LDA) was used to classify the regions as breast masses or normal tissue. In this article the overall detection results for two independent sets of 84 mammograms used alternately for training and test were evaluated by free-response receiver operating characteristics (FROC) analysis. The test results indicate that this new algorithm produced approximately 4.4 false positive per image at a true positive detection rate of 90% and 2.3 false positives per image at a true positive rate of 80%.

Image feature selection by a genetic algorithm: application to classification of mass and normal breast tissue

We investigated a new approach to feature selection, and demonstrated its application in the task of differentiating regions of interest (ROIs) on mammograms as either mass or normal tissue. The classifier included a genetic algorithm (GA) for image feature selection, and a linear discriminant classifier or a backpropagation neural network (BPN) for formulation of the classifier outputs. The GA-based feature selection was guided by higher probabilities of survival for fitter combinations of features, where the fitness measure was the area Az under the receiver operating characteristic (ROC) curve. We studied the effect of different GA parameters on classification accuracy, and compared the results to those obtained with stepwise feature selection. The data set used in this study consisted of 168 ROIs containing biopsy-proven masses and 504 ROIs containing normal tissue. From each ROI, a total of 587 features were extracted, of which 572 were texture features and 15 were morphological features. The GA was trained and tested with several different partitionings of the ROIs into training and testing sets. With the best combination of the GA parameters, the average test Az value using a linear discriminant classifier reached 0.90, as compared to 0.89 for stepwise feature selection. Test Az values with a BPN classifier and a more limited feature pool were 0.90 with GA-based feature selection, and 0.89 for stepwise feature selection. The use of a GA in tailoring classifiers with specific design characteristics was also discussed. This study indicates that a GA can provide versatility in the design of linear or nonlinear classifiers without a trade-off in the effectiveness of the selected features.

[Effects of wound wet dressing with cerium nitrate on cell-mediated immunity after severe burn]

Suppression of cell-mediated immunity (CM) and lowering of survival rate follow major thermal injury are associated with absorption of burn toxin. Wistar rats received 30% full-thickness burn, and were then treated with early burn excision or wet dressing of cerium nitrate for the wound. At day 14 postburn, both survival rates and peripheral blood Th/Ts rate were monitored. It was found that both excision and cerium nitrate could prevent marked lowering of survival rate and Th/Ts ratio were monitored. It was found that both excision and cerium nitrate could prevent markly lowering of survival rates and Th/Ts ratio induced by severe burn. This indicated that CE, in the early postburn days, may replace early burn excision to prevent the suppression of CMI following severe burn.

Site-specific excision repair of 1-nitrosopyrene-induced DNA adducts at the nucleotide level in the HPRT gene of human fibroblasts: effect of adduct conformation on the pattern of site-specific repair

Studies showing that different types of DNA adducts are repaired in human cells at different rates suggest that DNA adduct conformation is the major determinant of the rate of nucleotide excision repair. However, recent studies of repair of cyclobutane pyrimidine dimers or benzo[a]pyrene diol epoxide (BPDE)-induced adducts at the nucleotide level in DNA of normal human fibroblasts indicate that the rate of repair of the same adduct at different nucleotide positions can vary up to 10-fold, suggesting an important role for local DNA conformation. To see if site-specific DNA repair is a common phenomenon for bulky DNA adducts, we determined the rate of repair of 1-nitrosopyrene (1-NOP)-induced adducts in exon 3 of the hypoxanthine phosphoribosyltransferase gene at the nucleotide level using ligation-mediated PCR. To distinguish between the contributions of adduct conformation and local DNA conformation to the rate of repair, we compared the results obtained with 1-NOP with those we obtained previously using BPDE. The principal DNA adduct formed by either agent involves guanine. We found that rates of repair of 1-NOP-induced adducts also varied significantly at the nucleotide level, but the pattern of site-specific repair differed from that of BPDE-induced adducts at the same guanine positions in the same region of DNA. The average rate of excision repair of 1-NOP adducts in exon 3 was two to three times faster than that of BPDE adducts, but at particular nucleotides the rate was slower or faster than that of BPDE adducts or, in some cases, equal to that of BPDE adducts. These results indicate that the contribution of the local DNA conformation to the rate of repair at a particular nucleotide position depends upon the specific DNA adduct involved. However, the data also indicate that the conformation of the DNA adduct is not the only factor contributing to the rate of repair at different nucleotide positions. Instead, the rate of repair at a particular nucleotide position depends on the interaction between the specific adduct conformation and the local DNA conformation at that nucleotide.

[Improved MTT colorimetric assay for NKC activity]

The established improved 3-(4,5-dimethyl thiazoly)2,5-diphenyl-tetrazolium bromide (MTT) colorimetric assay for measuring the amount and function of living cell by the authors has the characteristics of simplicity, dependability and good repeatability within 3-12 hours. We have used this improved MTT colorimetric assay in measuring natural kill cell (NKC) activity of human peripheral blood. The results show that when the activities of effector cell (EC) and target cell (TC) are > or = 95%, and the density of EC is > or = 3 x 10(2)/well and that of TC > or = 1.6 x 10(2)/well, the number of living cell is positively correlated with the OD570nm volume of purple formazan metabolite of MTT solution (re = 0.94, ri = 0.97, P < 0.001). When the ratio of EC/TC is 40:1, the NKC activity of peripheral blood of health adults is equal to that report by Zhang Chongjie et al. By this MTT colorimetric assay, the NKC activity of peripheral blood of 10 leukemic patients has been detected. The mean +/- s of NKC activity is 34.86 +/- 7.80%, which is postively correlated with the result (35.16 +/- 8.40%) of the inhibition of 3H-TdR incorporation assay performed at the same time (r = 0.876, P < 0.001). MTT colormetric assay for NKC activity avoids getting in touch with isotope. It is a convenient and valuable method.

[Preparation and identification of monoclonal antibody GB2 directed against human breast cancer serum antigen]

Spleen cells from BALB/c mice immunized with human breast cancer serum antigen were fused with murine myeloma SP 2/0 cells. After screening with ELISA and limited-dilution cloning, one hybridoma which could stably secrete specific antibody was obtained and designated McAbGB2. The titer of McAbGB2 was up to 1.2 x 10(6) after purified by ammonium sulfate and DEAE-cellulose. The McAbGB2 was defined as murine IgG1 by agarose double immunodiffusiong. Immunoblotting analysis revealed that the antigens with molecular weights of 116 kd and 45 kd recognized by McAbGB2 were distributed in human breast cancer tissue and serum.

[Establishment of an effective way for separating and culturing tumor infiltrating lymphocytes]

The key to preparing TILs for clinical application is to enhance its capacity of proliferation and cytotoxicity. For this purpose we have made a study of methodology and established an effective way consisting of 3 processes to separate and culture TILs. It included: (1) mechanical splitting; (2) digesting with 0.05% collagenase I and 0.003% DNAase I mixture in room temperature for 6 hrs and 18hrs in cool, and (3) centrifuging with 75% and 100% Ficoll non-continuous grade density. The separated TILs were suspended in conditional culture medium for proliferation. Most of them reached the amount of 10(9) at the end of culture, which was essential for clinical therapy. Their NK and LAK activities were 56.3 +/- 11.7% and 48.6% +/- 10.6% respectively, in which the CD6+ T cells played an important role. The results suggest this a perfect way for separating and culturing TILs.

Classification of mass and normal breast tissue: a convolution neural network classifier with spatial domain and texture images

The authors investigated the classification of regions of interest (ROI's) on mammograms as either mass or normal tissue using a convolution neural network (CNN). A CNN is a backpropagation neural network with two-dimensional (2-D) weight kernels that operate on images. A generalized, fast and stable implementation of the CNN was developed. The input images to the CNN were obtained from the ROI's using two techniques. The first technique employed averaging and subsampling. The second technique employed texture feature extraction methods applied to small subregions inside the ROI. Features computed over different subregions were arranged as texture images, which were subsequently used as CNN inputs. The effects of CNN architecture and texture feature parameters on classification accuracy were studied. Receiver operating characteristic (ROC) methodology was used to evaluate the classification accuracy. A data set consisting of 168 ROIs containing biopsy-proven masses and 504 ROI's containing normal breast tissue was extracted from 168 mammograms by radiologists experienced in mammography. This data set was used for training and testing the CNN. With the best combination of CNN architecture and texture feature parameters, the area under the test ROC curve reached 0.87, which corresponded to a true-positive fraction of 90% at a false positive fraction of 31%. The authors' results demonstrate the feasibility of using a CNN for classification of masses and normal tissue on mammograms.

An adaptive density-weighted contrast enhancement filter for mammographic breast mass detection

Presents a novel approach for segmentation of suspicious mass regions in digitized mammograms using a new adaptive density-weighted contrast enhancement (DWCE) filter in conjunction with Laplacian-Gaussian (LG) edge detection. The DWCE enhances structures within the digitized mammogram so that a simple edge detection algorithm can be used to define the boundaries of the objects. Once the object boundaries are known, morphological features are extracted and used by a classification algorithm to differentiate regions within the image. This paper introduces the DWCE algorithm and presents results of a preliminary study based on 25 digitized mammograms with biopsy proven masses. It also compares morphological feature classification based on sequential thresholding, linear discriminant analysis, and neural network classifiers for reduction of false-positive detections.

Comparison of body surface potential maps simulated with isotropic and anisotropic computer heart models

Simulated body surface potential maps (SBSPM) with isotropic and anisotropic heart models were compared to investigate the effect of myocardial anisotropy on body surface electrocardiograms at a whole heart level. Rotative fiber orientations of total 90 degrees was incorporated into an isotropic heart model. The anisotropy of conduction velocity and intracellular electric conductivity was included in the simulation. SBSPM based on epicardial, intramural, and endocardial stimulation show high correlation with fiber orientations. On the other hand, the anisotropy cannot be distinguished from the SBSPM in the simulation of normal heart model.

[Tuberculosis in chronic renal failure patients with or without renal replacement therapy]

Tuberculosis developed in 40 out of 978 chronic renal failure (CRF) patients with or without renal replacement therapy during a five-year period. The incidence was 4.1% and was 10 times higher than that in the general population. The onset of symptoms was within 1 year after dialysis or kidney transplantation in 68% of the patients. 82.5% of them had predominantly extrapulmonary tuberculosis and most of these were lymph node infection. The diagnosis of tuberculosis in these patients was difficult; tuberculin sensitivity was present only in 6.4% of the patients and examination of sputum and other fluid for mycobacteria was usually unrewarding. Detecting serum anti-PPD-IgG level might be a valuable supplementary diagnostic method, because 85% of patients with active tuberculosis showed positive results. Measuring serous exudate and urine anti-PPD-IgG level by ELISA or M. Tuberculosis DNA by PCR might be helpful in the diagnosis of tuberculous serositis and urinary tract mycobacterial infection.

Classification of mass and normal breast tissue on digital mammograms: multiresolution texture analysis

We investigated the feasibility of using multiresolution texture analysis for differentiation of masses from normal breast tissue on mammograms. The wavelet transform was used to decompose regions of interest (ROIs) on digitized mammograms into several scales. Multiresolution texture features were calculated from the spatial gray level dependence matrices of (1) the original images at variable distances between the pixel pairs, (2) the wavelet coefficients at different scales, and (3) the wavelet coefficients up to certain scale and then at variable distances between the pixel pairs. In this study, 168 ROIs containing biopsy-proven masses and 504 ROIs containing normal parenchyma were used as the data set. The mass ROIs were randomly and equally divided into training and test groups along with corresponding normal ROIs from the same film. Stepwise linear discriminant analysis was used to select optimal features from the multiresolution texture feature space to maximize the separation of mass and normal tissue for all ROIs. We found that texture features at large pixel distances are important for the classification task. The wavelet transform can effectively condense the image information into its coefficients. With texture features based on the wavelet coefficients and variable distances, the area Az under the receiver operating characteristic curve reached 0.89 and 0.86 for the training and test groups, respectively. The results demonstrate that a linear discriminant classifier using the multiresolution texture features can effectively classify masses from normal tissue on mammograms.

Computer-aided classification of mammographic masses and normal tissue: linear discriminant analysis in texture feature space

We studied the effectiveness of using texture features derived from spatial grey level dependence (SGLD) matrices for classification of masses and normal breast tissue on mammograms. One hundred and sixty-eight regions of interest (ROIS) containing biopsy-proven masses and 504 ROIS containing normal breast tissue were extracted from digitized mammograms for this study. Eight features were calculated for each ROI. The importance of each feature in distinguishing masses from normal tissue was determined by stepwise linear discriminant analysis. Receiver operating characteristic (ROC) methodology was used to evaluate the classification accuracy. We investigated the dependence of classification accuracy on the input features, and on the pixel distance and bit depth in the construction of the SGLD matrices. It was found that five of the texture features were important for the classification. The dependence of classification accuracy on distance and bit depth was weak for distances greater than 12 pixels and bit depths greater than seven bits. By randomly and equally dividing the data set into two groups, the classifier was trained and tested on independent data sets. The classifier achieved an average area under the ROC curve, Az, of 0.84 during training and 0.82 during testing. The results demonstrate the feasibility of using linear discriminant analysis in the texture feature space for classification of true and false detections of masses on mammograms in a computer-aided diagnosis scheme.

[Treatment of severe burn of knee joint with fasciocutaneous flap of the lower leg]

Burn of knee joint often happens on the extended side surface and hurts the articular capsule and cavity. Five patients with severe burn of knee joint were successfully treated with fasciocutaneous flap of the lower leg. After the operation, all the flaps survived. Three patients' articular cavity got initial sealing-up. Except two patients' joints merging, joint movement was normal or near normal, and with satisfactory appearance. The timing, key points, and advantages of this operation were discussed. The fasciocutaneous flap of the lower leg is a good selection for severe burn of knee joint.

Comparative simulation of excitation and body surface electrocardiogram with isotropic and anisotropic computer heart models

Comparative simulations between isotropic and anisotropic computer heart models were conducted to study the effects of myocardial anisotropy on the excitation process of the heart and on body surface electrocardiogram. The isotropic heart model includes atria, ventricles, and a special conduction system, and is electrophysiologically specified by parameters relative to action potential, conduction velocity, automaticity, and pacing. The anisotropic heart model was created by incorporating rotating fiber directions into the ventricles of the isotropic heart model. The orientation of the myocardial fibers in the ventricles of the model was gradually rotated counterclockwise from the epicardial layer to the endocardial layer for a total rotation of 90 degrees. The anisotropy of conduction velocity and intracellular electric conductivity was included in the simulation. Comparative simulations of the normal heart, LBBB, and RBBB showed no significant differences between the two models in the excitation processes of the whole heart or in the body surface electrocardiograms. However, it was easier to induce ventricular fibrillation in the anisotropic model than in the isotropic model. The comparative simulation is useful for investigating the effects of myocardial anisotropy at the whole heart level and for evaluating limitations of the isotropic heart model.

Site-specific rates of excision repair of benzo[a]pyrene diol epoxide adducts in the hypoxanthine phosphoribosyltransferase gene of human fibroblasts: correlation with mutation spectra

When populations of repair-proficient diploid human fibroblasts were treated with (+/-)-7 beta, 8 alpha-dihydroxy-9 alpha, 10 alpha-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene (BPDE) during early S phase, just as the hypoxanthine phosphoribosyltransferase gene (HPRT) was being replicated, 5% of the induced base substitutions were found at nt 212, and 5% of the substitutions were found at nt 229 in exon 3. However, when the population was treated in early G1 phase to allow at least 12 hr for repair before the onset of S phase, 21% of the substitutions were found at nt 212, and 10% were found at nt 229. No such cell-cycle-dependent difference in distribution of base substitutions occurred in excision-repair-deficient cells. To test whether the increase in the relative frequency of mutations resulted from inefficient repair at these sites, we adapted ligation-mediated PCR to measure the rates of removal of BPDE adducts from individual sites in exon 3 of the HPRT gene. Cells were treated with 0.5 microM BPDE in early G1 phase and harvested immediately or after 10, 20, and 30 hr for repair. the nontranscribed strand of exon 3 was analyzed for the original distribution of adducts and those remaining after repair, using Escherichia coli UvrABC excinuclease to excise the adducts and annealing a 5' biotinylated gene-specific primer to the DNA and extending it with Sequenase 2.0 to generate a blunt end at the site of each cut. A linker was ligated to the blunt end, and the desired fragments were isolated from the rest of the genomic DNA by using magnetic beads, amplified by PCR, and analyzed on a sequencing gel. The distribution of fragments of particular lengths indicated the relative number of BPDE adducts initially formed or remaining at specific sites. The rates of repair at individual sites varied widely along exon 3 of the HPRT gene and were very slow at nt 212 and 229, strongly supporting the hypothesis that inefficient DNA repair plays an important role in the formation of mutation hotspots.

Cortical cerebral blood flow cycling: anesthesia and arterial blood pressure

Cycling of various cerebral metabolic substances, arterial vascular diameter, and flow has been noted by many workers at a frequency near 0.1 Hz. Suspicion that this phenomenon is dependent on the type of anesthesia led us to investigate the occurrence of cerebral blood flow (CBF) cycling with different anesthetics. Fifteen Sprague-Dawley rats were anesthetized with either pentobarbital (n = 5, 40-50 mg/kg), alpha-chloralose (n = 5, 60 mg/kg), or halothane (n = 5, 1-0.5%). Body temperature was maintained at 37 degrees C. Femoral arterial and venous catheters were placed, and a tracheotomy was performed, permitting artificial ventilation with 30% O2-70% N2. A closed cranial window was formed over a 3-mm diameter craniotomy. Mean arterial pressure (MABP), arterial partial pressures of CO2 and O2 (PaCO2 and PaO2), and pH were controlled and stabilized at normal values. CBF was determined using laser Doppler flowmetry. To induce cycling, MABP was transiently and repeatedly lowered by exsanguination. Fast Fourier analysis of selected 64-s flow recordings (n = 38) was performed. CBF cycling was observed, independent of the type of anesthesia, in all animals. In 36 epochs, cycling was induced when MABP was reduced to a mean pressure of 65 +/- 1.5 mmHg. The mean frequency and amplitude were 0.094 +/- 0.003 Hz and 6.6 +/- 0.5%, respectively. Cycling occurred without blood withdrawal in two epochs. With the use of the blood-withdrawal epochs (n = 36), all three anesthetics shared a common linear slope between amplitude and blood pressure (P < 0.02) and blood pressure change (P < 0.01). Pentobarbital differed from alpha-chloralose and halothane in the relation between cycling frequency and blood pressure. Only pentobarbital exhibited correlation between frequency and blood pressure (P < 0.02) and blood pressure change (P < 0.001). The occurrence of these oscillations is not related to the type of anesthesia, and they usually occur at MABP values that are near or just above the lower limit of autoregulation. At this pressure level, CBF oscillations would suggest that vasoconstrictive and dilatory forces are no longer in balance, but alternatively vying for control.

Estimation of cerebral blood flow from thermal measurement

A thermal method has been developed to quantify continuous perfusion changes with self-calibration. A dynamic, one-dimensional bio-heat transfer model of the thermal probe and tissue describes the system response to either continuous or transient heating. A nonlinear least-squares fit of the model to experimental data yields estimates of the baseline perfusion and other model parameters. With a partial analytical solution of the model, the optimal estimation procedure is two orders of magnitude more efficient than with a total numerical solution of the model system. Experimental data is used to estimate the operating relations between perfusion and the temperature measurement. A new procedure has also been presented to obtain the dynamic response of the system for continuous measurement of perfusion.

[Early diagnosis of tuberculosis after kidney transplantation by determining serum anti-PPD-IgG]

Tuberculosis is a common complication after kidney transplantation and is not easy to diagnose in the early stage. Determination of serum anti-PPD-IgG level in our laboratory indicated that it was positive in patients with active tuberculosis. The mean time (20.5 days) required to diagnose with this method was obviously shorter than that (66.8 days) required with bacteriology, pathology or imaging. There was no obvious rise in the serum level of anti-PPD-IgG in fever caused by other infections and rejection and the serum anti-PPD-IgG level in patients with tuberculosis controlled returned to normal. It is shown that determination of serum specific antibody is a better index for early diagnosis of tuberculosis complicating kidney transplantation.

[Development of a monoclonal antibody (AF9) to human breast carcinoma]

A monoclonal antibody AF9 (IgG1) was raised against human breast carcinoma by fusing murine myeloma SP2/0 cells with spleen cells from BALB/c mice immunized with cell membrane extracts from primary breast carcinoma. Immunohistochemical staining using the antibody showed reactivity in 19 out of 20 breast carcinoma tissues and in some nonbreast carcinomas such as hepatic, ovarian, lung, colon, and gastric carcinoma tissues. But no staining was observed in either normal tissues or other carcinomas. By immunological treatment, the antigen recognized by AF9 was referred to be glycoprotein with lipid component, and Western blotting revealed that its molecular weight is 51, 56, 67 and 73kd.

Human endothelial cells are defective in diabetic vascular disease

Diabetic vascular disease is characterized pathologically by endothelial cell (EC) hyperplasia and basement membrane (BM) thickening. One key question regarding the pathogenesis of diabetic vascular disease is whether the EC or BM or both are primarily defective and responsible for these pathological changes. Previous studies, which took the approach of creating artificial diabetic conditions, have been inconclusive. It is known, however, that the extracellular matrix may be altered by glycosylation as a result of hyperglycemia, thereby altering EC function. To begin to address this question and more closely mimic the situation in vivo, we characterized human diabetic EC harvested from insulin-dependent diabetic mothers (IDDM) at the cellular and molecular levels. Human EC were isolated from both normal and IDDM umbilical cords and cellular functions evaluated using standard assays of attachment (% attached cells), proliferation (cpm/cell), resistance to detachment under shear stress (number of cells remaining attached), and glucose uptake (cpm/2 X 10(4) cells). Gene expression of major BM components (collagen type IV, laminin beta 1, and laminin beta 2) was quantified by Northern analysis. Diabetic EC demonstrated increased proliferation (two- to eightfold compared to normals), were 20-40% less resistant to shear stress and took up glucose 10-15% more slowly than normal EC. Furthermore, Northern analysis showed that the expression of major BM components was increased by an average of 10-18% in diabetic cells compared to normal cells. These results were consistent with in vivo observations and previously published data.(ABSTRACT TRUNCATED AT 250 WORDS)

Thermal method for continuous measurement of cerebral perfusion

A new thermal system using constant heating power for continuous measurement of cerebral perfusion is presented. It is designed and implemented for optimal perfusion sensitivity and dynamic response based on heat-transfer analysis of perfused brain tissue with thermistors on the cortical surface. Two matched thermistors are used, one to serve as a perfusion sensor and the other to compensate for the base-line temperature changes. To improve the signal-to-noise ratio of the measurement system, lock-in amplifiers are used to minimise long-term drift and low-frequency noise. Errors in the measurement caused by electrical and thermal fluctuations are tested and analysed. In vitro tests show that the measurement accuracy of temperature change is better than 10(-3) degrees C, and the temperature resolution is even greater. In vivo evaluation confirms that the system is responsive to cerebral perfusion changes associated with sudden changes in mean arterial blood pressure caused by bolus injection of norepinephrine, blood withdrawal and blood infusion. The dynamic response of the system is sufficient to detect the autoregulatory perfusion changes in response to arterial blood pressure alteration and the oscillations of cerebral blood flow.

The spectrum of chronic lymphoproliferative disorders in Chinese people. An analysis of 64 cases

BACKGROUND

Chronic lymphoproliferative disorders are considered rare in Oriental patients and are thought to constitute only 2% of all leukemias in these patients, compared to 20-30% in Western patients. We conducted a retrospective analysis of Chinese patients with chronic lymphoproliferative disorders to define the frequency and spectrum of these disorders.

METHODS

A consecutive series of Chinese patients with leukemia and lymphoproliferative disorders seen at two regional hospitals in Hong Kong were analyzed retrospectively. The diagnosis of chronic lymphoproliferative disorders was based on morphologic and immunologic criteria proposed by the French-American-British Cooperative Study Group.

RESULTS

Sixty-four Chinese patients with chronic lymphoproliferative disorders were identified, and these patients constituted 19% of a total of 342 cases of leukemia diagnosed in 3 years. Chronic lymphocytic leukemia was the most common form, occurring at a frequency of 12.5% of all leukemias. The clinicopathologic features of these patients were similar to those of Western patients, except that Chinese patients tended to present with more advanced (Rai's Stages III and IV; Binet's Stage C) and bulky (splenomegaly > 9 cm) disease, and expressed lambda light chain about six times more frequently. Other chronic lymphoproliferative disorders identified in this study included prolymphocytic leukemia, mantle zone lymphoma, hairy cell leukemia, splenic lymphoma with villous lymphocytes, large granular lymphocyte leukemia, and Sezary syndrome. The authors did not identify any case of human T-cell lymphotropic virus-I-related lymphoproliferative disorders within the study period.

CONCLUSION

In addition to providing the frequencies of various chronic lymphoproliferative disorders in southern Chinese people, this study also showed that these disorders no longer should be considered rare in this population. Inherent biologic differences between lymphoproliferative disorders in Chinese and Western patients also may exist.

Quantitative analysis of the cardiac reserve

OBJECTIVES

Analysis of the left ventricular (LV) pressure-volume loop (P-V loop) to assess LV function.

DESIGN

Retrospective study of clinical, hemodynamic and angiographic data of 29 normal individuals and 115 patients with myocardial dysfunction, but no valvular or congenital heart disease. P-V loops were constructed, critically analyzed and compared with the clinical functional status of the patients.

MAIN RESULTS

A number of theoretical new concepts was introduced and measured: end-systolic energy (ESE), total LV energy (TE) and potential maximal LV energy (PEmax). These variables were compared with the stroke work, which is neither sensitive nor specific, to separate different stages of cardiac function. ESE, TE and PEmax are sensitive variables, and inversely related to the cardiac reserve.

CONCLUSIONS

P-V loops are easy to construct using well recorded hemodynamic and angiographic data. Analysis of P-V loops provides the cardiologist with an overall picture of the myocardial function and reserve.

High incidence of thrombophilia detected in Chinese patients with venous thrombosis

Venous thromboembolism is rare in Chinese. To determine the incidence and disease profile of thrombophilia in Chinese patients with thrombosis, 52 unselected Chinese patients with documented venous thrombosis were studied for the presence of thrombophilia. Levels of antithrombin III (AT III), protein C (PC) and protein S (PS) as well as the presence of acquired lupus anticoagulant (LA) and anticardiolipin antibody (ACA) were investigated. Thirty patients were found to be abnormal. These consisted of 5 AT III deficiencies, 9 PC deficiencies, 10 PS deficiencies, 1 combined PC & PS deficiency (all in the heterozygous range), and 5 patients with LA and/or ACA. When the patients with LA and/or ACA are excluded, the incidence of hereditary thrombophilia is 25/47 i.e. 53.2% which is much higher than those reported in studies of Caucasian patients selected under strict criteria. Family studies performed in 16 cases of hereditary thrombophilia revealed involvement in 11 cases (68.7%); a total of 36 heterozygous family members were affected, most of which remain asymptomatic. Although 35 events predisposing to thrombosis (27 pregnancies, 1 oral contraceptive consumption and 7 surgical operations) were identified among these index patients, and the heterozygous family members, thrombosis was observed on only 6 occasions (17.1%). The data suggest that pregnancy and surgery do not carry the same degree of thrombotic risk in Chinese as in the Caucasian population with heterozygous AT III, PC and PS deficiency.

Philadelphia chromosome positive acute lymphoblastic leukemia masquerading as persistent asymptomatic bone marrow necrosis

Bone marrow necrosis is an uncommon histologic finding of malignant diseases at presentation. Clinically it is characterized by pyrexia and severe bone pain, and heralds a poor prognosis if untreated. We report an unusual patient with asymptomatic bone marrow necrosis persisting for 10 mths, a hitherto undescribed length of time for this condition. The diagnosis of Philadelphia chromosome positive acute lymphoblastic leukemia was finally made after multiple bone marrow biopsies.

Isolation and characterization of early pregnancy factor

Early pregnancy factor (EPF) was purified from the pooled sera of 210 pregnant women at 3-8 weeks of gestation. Sera from healthy nonpregnant women were used as control. The samples (G-II, G-III and G-IV) obtained from pregnant women had EPF activity but no HCG activity. Polyacrylamide gel electrophoresis showed that the major bands in pregnant G-III and G-IV were at similar positions in tube gels. The results of SDS-PAGE showed 3 bands in pregnant G-IV: 57.0 kD, 38.0 kD and 19.0 kD. The basic active form of EPF may be a small peptide of 19.0 kD. The isoelectric points of pregnant G-IV were 6.45 and 8.20.

Validation of continuous thermal measurement of cerebral blood flow by arterial pressure change

A thermal measurement system to monitor cerebral blood flow (CBF) continuously from the cortical surface is evaluated in vivo. It has a temperature resolution of better than 0.001 degrees C (1 m degrees C) and can compensate for baseline temperature fluctuations in the brain tissue. A new approach has been developed to test the capability of monitoring dynamic CBF response. Transient CBF changes associated with changes in mean arterial blood pressure (MABP) caused by repeated bolus norepinephrine injections are used to examine the response of the measurement system in both the heated mode, sensitive to flow, and the unheated mode, sensitive only to temperature. Experiments on 13 rats demonstrate that changes in the MABP are closely correlated with those of temperature difference in the heated mode. Regression analysis shows a mean slope of 0.9 m degrees C/mm Hg in the heated mode, which is significantly different from zero (p < 0.002) and from the mean slope in the unheated mode (p < 0.002). This indicates that flow signal in the system output can be distinguished from the baseline thermal fluctuations. Thus, the system can be used to detect and study dynamic perfusion changes from the brain surface with minimal tissue damage. Furthermore, analysis of the data shows that the transient flow signal before autoregulation is linearly correlated with changes in MABP.

Soft X-ray microimages of immunogold-labelled tumor cell surface antigens

After successfully introducing the colloidal immunogold labelling technique to soft X-ray contact microscopy (SXCM), SXCM replica microimages of immunogold labelled tumor cell HLA-A2 surface antigens have been acquired for the first time. A biological sample preparation method using immunocytochemical staining techniques suitable for SXCM has also been established.

Extended Kalman filter (EKF) application in vitamin C two-step fermentation process

Based on kinetic model study of vitamin C two-step fermentation, the extended Kalman filter (EKF) theory is conducted for studying the process which is disturbed by white noise to some extent caused by the model, the fermentation system and operation fluctuation. EKF shows that calculated results from estimated process parameters agree with the experimental results considerably better than model prediction without using estimated parameters. Parameter analysis gives a better understanding of the kinetics and provides a basis for state estimation and state prediction.

Near-octaploidy in essential thrombocythemia

We report a case of essential thrombocythemia which on cytogenetic analysis showed an abnormal clone with near-octaploidy. Such hyperploidy is extremely unusual in clonal hematologic abnormalities. The possible significance of this finding is discussed.

Study on the genesis of giant negative T wave in apical hypertrophic cardiomyopathy using a three-dimensional computer model

Apical hypertrophic cardiomyopathy is characterized by a spade-like left ventricular cavity and by both giant negative T waves and tall R waves in the electrocardiogram. However, the mechanisms of these ECG abnormalities have not been satisfactorily clarified. We have recently developed a three-dimensional computer model of ventricular depolarization and repolarization processes. This model has successfully simulated normal QRST waves and changes characterizing some abnormal conditions. A model of apical hypertrophic cardiomyopathy was constructed by adding model units to the endocardium of the left ventricular apex. The surface ECG was then calculated by assuming different gradients of action potential durations and different proportions of the hypertrophic cells in the apical segment. A negative T wave of -1.45 mV in lead V4, similar to the clinically reported ECG, was obtained by assuming: (1) diffusely distributed hypertrophic cells at the apex and (2) uniform, long action potential durations of hypertrophic cells. It is suggested that these properties may account for the distinctive ECG abnormalities in apical hypertrophic cardiomyopathy.

Correction of anemia in patients on continuous ambulatory peritoneal dialysis with subcutaneous recombinant erythropoietin twice a week: a long-term study

Subcutaneous recombinant human erythropoietin (rHuEPO) was given for 12 months twice weekly to 10 patients on continuous ambulatory peritoneal dialysis (CAPD) with anemia (hemoglobin less than 9.0 mg/dl). All patients responded to a median weekly dose of between 37.5 to 100 (mean 55 to 105) units/kg and reached a target hemoglobin of 10-12 mg/dl in a mean of 11.7 weeks (range 5-24). Serum iron, iron saturation and ferritin were significantly lower and serum potassium was significantly higher than the pre-treatment level from 1 month onwards. Five patients without pre-treatment iron overload required oral iron supplement and 3 required oral potassium-binding resin. No significant change in other serum biochemical parameters was observed. Blood pressure remained stable during the treatment period but additional or increased dosage of antihypertensive drugs was required in 5 patients. Peritoneal small solute clearance and ultrafiltration and residual renal clearance did not change significantly after correction of anemia. The incidence of peritonitis and exit site infection was similarly unaffected. One patient developed a severe headache which was not associated with hypertension and responded to withdrawal of rHuEPO treatment. Most of the remaining patients showed improvement in subjective well-being. It was concluded that the subcutaneous route twice a week is a safe, convenient and cost-effective way to administer rHuEPO to patients on CAPD.

[Different effects on dopamine receptors D1 and D2 following long-term usage of L-dopa]

Different effects on D1 and D2 receptor subtypes were studied through observation of animal behavior, striatal receptor binding, and micro-electrode recording of cell activity in substantia nigra pars compacta of rats. The authors investigated the relation between dynamic changes of D1 and D2 receptor subtypes and the animal behavior, and speculate on the possible mechanisms of deterioration of drug effect and appearance of AIM induced by DA agonists during the treatment of Parkinson's disease.